Fireblocks Java SDK 10.1.0: Deserialization Error When Retrieving ERC20 Token Contract Address

Developer Discussion
1

Hi,

I’m trying to perform a mint operation for the ETH_TEST5 ERC20 token using the Fireblocks Java SDK (version 10.1.0). To do this, I first need to retrieve the token contract address from the Fireblocks API:

Endpoint:
GET https://sandbox-api.fireblocks.io/v/tokenization/tokens/29e93a40-7971-4c16-99b7-83e6df097af3

Sample response:

{
    "id": "29e93a40-7971-4c16-99b7-83e6df097af3",
    "displayName": "Unit Test Token 30/05/2025 15:47",
    "status": "COMPLETED",
    "type": "FUNGIBLE_TOKEN",
    "refId": "UTT_TEST_B75VRLGX_49CE",
    "tokenMetadata": {
        "assetId": "UTT_TEST_B75VRLGX_49CE",
        "name": "Unit Test Token 30_05_2025 15_47",
        "symbol": "UTT_TEST",
        "testnet": true,
        "networkProtocol": "ETH",
        "contractAddress": "0x987355F9439F2DfB883bbC99Aa098AD93975a3c8",
        "blockchain": "ETH_TEST5",
        "decimals": 18,
        "type": "ERC20",
        "totalSupply": "0",
        "vaultAccountId": "1"
    }
}

When I call the SDK method:

TokenLinkDto data = fireblocks.tokenization().getLinkedToken(idToken).join().getData();

I get the following error:

java.util.concurrent.CompletionException: com.fireblocks.sdk.ApiException: com.fasterxml.jackson.databind.JsonMappingException: Unexpected IOException (of type java.io.IOException): Failed deserialization for TokenLinkDtoTokenMetadata: 3 classes match result, expected 1

After checking the code, I found that the deserializer (TokenLinkDtoTokenMetadataDeserializer) tries to match the tokenMetadata JSON to one of three classes (AssetMetadataDto, CollectionMetadataDto, ContractMetadataDto). In this case, the JSON matches all three, so the deserializer fails with “3 classes match result, expected 1”.

Has anyone faced this issue? Is there a recommended workaround or patch for the SDK? Should I update the library, or is there a way to customize the deserialization logic to handle this ambiguity?

Thanks in advance for any suggestions!